One common illuminating device that uses solar energy for gardening or decoration purpose is as shown in FIG. 1A. Such an illuminating device has a solar panel 91 provided outside a lamp cover 93. However, such an arrangement occupies a lot of space and is unesthetic. Further, as the solar panel 91 is exposed to outside the lamp cover, it is prone to be damaged by weather or inappropriate operation of user. Besides, as the solar panel 91 is located at a lower altitude, it tends to be blocked by the surrounding plants or objects, and the power generating efficiency thereof is seriously affected.
To overcome the above defect, it has been suggested to incorporate the solar panel 91 with the light source 92 inside the lamp cover 93. Such arrangement may reduce the occupying space, and protect the solar panel 91. However, as the volume of the solar panel 91 increases, not only the volume of the lamp cover 93 has to be increased accordingly, but also the opening 931 for the access of the solar panel at the bottom of the lamp cover 93 has to be enlarged to an extent for allowing the solar panel 91 to pass through. Accordingly, the volume of the illuminating device will be increased, and the base device mounted at the opening becomes bulky, giving an unaesthetic appearance to the lamp, which is disadvantageous to the gardening or decoration arrangement.